1. Field of the Invention
The invention concerns a telecommunication network with separate call control and connection control.
In what follows, the expression "call control" refers to all network functions which process requests for service sent by a subscriber. Thus call control has an overview of all the resources of a switching node that will be required to set up a call. The expression "connection control" refers to all functions required to set up connections: setting up, supervising and clearing down the connections supporting a call. Thus connection control includes switching functions and routing functions.
2. Description of the Prior Art
In a known model of the narrowband integrated services digital network (ISDN) call control and connection control are not separated: setting up a call involves simultaneous connection control and call control. A model has been developed for a first set of intelligent network services. This model does not call into question the narrowband ISDN model but rather adds to it a service control model for controlling the narrowband ISDN model during certain call phases.
This model added to the narrowband ISDN model is used in the mobile radio network described in French patent application n.degree. 2 638 307, for example. In this network a switching center includes a service switching point implementing only voice and data switching functions and a mobile radio control point implementing only signalling functions concerned with mobile radio subscriber mobility (roaming). Mobile radio subscriber call control is therefore effected in the switch which is a conventional switching center part of which is used to connect fixed subscriber terminals.
A model for broadband basic services has been developed. This model is based on the principle of separating call control and connection control. It therefore differs fundamentally from the model of the intelligent network added to the model of the narrowband ISDN. The multimedia call concept makes it essential to distinguish between call control and connection control because call set-up may be followed by the setting up of multiple connections which may vary during the same call. A broadband call may be conveyed by a unidirectional connection and subsequently by a bidirectional connection, for example, or its bandwidth may change depending on the services requested during one and the same call.
The model of the broadband network for basic services is inadequate for multiparticipant calls and for processing sophisticated services such as multimedia services.
An object of the invention is to propose a telecommunication network able to support sophisticated services including broadband sophisticated services.